Mixed-focus collaboration occurs when people work on individual
tasks in a shared space - and although their tasks may not be
directly linked, they still need to maintain awareness and manage
access to shared resources. This kind of collaboration is common
on tables, where people often use the same space to carry out work
that is only loosely coupled. At physical tables, people easily
manage to coordinate access to the table surface and the artifacts
on it, because people have years of experience interacting around
other physical bodies. At distributed digital tabletops, however,
where there is no physical body for the remote person, many of the
natural cues used to manage mixed-focus collaboration are missing.
To compensate, distributed groupware often uses digital
embodiments. On digital touch tables, however, we know little
about how these embodiments affect coordination and awareness.
We carried out an empirical study of how four factors in an arm
embodiment (transparency, input technique, visual fidelity, and
tactile feedback) affected implicit coordination, awareness, and copresence.
We found that although some embodiments affected
subjective feelings of co-presence or awareness, there were no
changes in table behavior - people acted as if the other person did
not exist. These findings show the possibilities and limitations of
digital arm embodiments, and suggest that the natural advantages
of tables for collaboration may not extend to distributed tables.